FRUITS REPLACED BY OFFSHOOTS. 459 



Cirsium heterophyllum and spinosissimum, and Cirsium affine, a hybrid between 

 C. heterophyllum and 0. oleraceum, are very abundant in many Alpine valleys, 

 and one may find more examples of these hybrids than of their parents in many 

 a meadow. Several of the Fuller's Thistle hybrids, the parents of which are 

 biennial, become perennial by a production of lateral shoots from the leaf -axils at 

 the base of the stem. Here also, as with climatic conditions, we find vegetative 

 propagation replacing fruit-production. 



There are also many species, of which it cannot be definitely asserted that 

 they have arisen by hybridization in recent times, which fruit but seldom even 

 when the climatic conditions are in every way favourable for this kind of repro- 

 duction. According to agriculturists, there are many kinds of Potato which flower 

 only occasionally but do not ripen fruit, although the flowers and pollen-grains 

 appear quite normal. It is just these Potatoes which are characterized by their 

 rich production of tubers, fruit-formation being in them replaced by vegetative 

 propagation. 



That plants, with double flowers, the ovaries of which, under the influence of 

 little insects (Phytopus), have undergone a deep-reaching transformation, should 

 ripen no fruits is to be expected and has long been known, as also is the fact that 

 these plants produce buds and offshoots freely. Of special note in this connection 

 is a Bitter-cress (Cardamine uliginosa) often met with in damp meadows in the 

 neighbourhood of Vienna, Salzburg, and Ried, growing wild with double flowers. 

 On most of the plants, the fruits of which are abortive, those curious leaf-buds, 

 represented in fig. 200 4 , p. 41, are to be found. 



Again, with many species of plants, it may come to pass that the insects which 

 should accomplish their pollination are now no longer prevalent in the region 

 where the plants grow, or indeed have entirely deserted them. This category of 

 plants obviously includes only such forms as are destitute of arrangements for 

 promoting autogamy, in the case of cross-pollination not taking place. In a very 

 considerable number of these plants, flowers and fruits are replaced by offshoots 

 offshoots of the most varied kinds, including aerial and subterranean tubers, 

 bulbils, green leafy shoots, and, in rare cases, little bud-like structures, from each 

 of which a thick, fleshy root arises in such a manner that the greater part of the 

 offshoot consists of a root. 



As all these varieties of offshoots will be dealt with in a later chapter devoted 

 to the distribution of such structures by wind, animals, and special mechanisms, it 

 must suffice to speak here of a very few cases. Growing in sunny spots, the 

 yellow flowers of the Lesser Celandine (Ranunculus Ficaria) are occasionally 

 visited by little pollen-eating beetles, by flies and bees; under these circumstances 

 heads of fruit are ripened here and there from the flowers. But in shady places, 

 beneath bushes, and on the dark forest floor, these insect- visits are much rarer, 

 and almost all the flowers fail to ripen fruit. These shaded plants, however, 

 develop little bulbous bodies in the axils of their upper foliage-leaves, which 

 become detached on the withering of the shoot and give rise to new plants (see 



